This invention relates to a closure to be attached to a container for containing a fluid such as a liquid food, seasoning, detergent, etc. (hereinafter referred to as "contents").
A conventional container for containing contents as above is provided in the form of, for example, a plastic bottle or by, for example, fusion of soft synthetic resin sheets, and has a closure of a synthetic resin through which the contents come out. This closure has a function of sealing the contents in the container when they are being sold, and re-sealing the container after it is once opened.
The re-sealing function of the conventional closure is realized by a structure which consists of a plurality of closure members (a so-called two-piece structure is well known). In a case where such a two-piece closure is attached to a plastic bottle, it comprises a main body to be attached to the opening of the bottle, and a cap which can be attached to and detached from the main body. The main body has a closing section of a thin thickness provided with a score line and disposed to close the opening of the bottle. The closing section is provided with a pinch section which facilitates ripping of the closing section along the score line. The bottle opening is opened along the score line by pinching the pinch section and ripping the closing section along the line. After the contents are taken out of it, the bottle is again sealed by attaching the cap to the main body of the closure.
The conventional closure with the re-sealing function has the aforementioned two-piece structure and is therefore inevitably expensive. Moreover, since the opening is formed by ripping the closing section of the main body along the score line provided therein, there exists a space between the opening and the cap, into which the liquid may easily leak or drip. This is inconvenient during use.
To avoid it, it is considered to impart to the closure a one-piece structure in which those structural members are formed integral with each other as one body. However, it is difficult to construct the closure such that the main body and the cap can be easily and reliably separated from each other during use, and be reliably coupled to each other in a liquid-tight manner.
In other words, if both the main body and the cap cannot be separated unless a strong force is applied thereto, or if they are separated at inappropriate portions thereof when the user has handled the closure in an optional manner, the closure will be hard for the user to handle.